Two-way outdwelling slit valving of medical liquid flow through a cannula and methods

ABSTRACT

A cardiovascular outdwelling, normally closed, pressure-responsive slit valve liquid flow control and related methods wherein a diaphragm having a slit therein is flexed distally by hydrostatic pressure and proximally by negative pressure at different points in time to selectively open the slit and accommodate the flow of IV solution to a medical patient through a cannula and blood sampling from the cardiovascular system of the patient through the cannula in such a way as to prevent bleed-back and clotting of blood within the cannula.

This application is a continuation of our co-pending U.S. patentapplication Ser. No. 776,927, filed Oct. 15, 1991, now U.S. Pat. No.5,169,393 which is a continuation of our U.S. patent application Ser.No. 577,941, filed Sep. 4, 1990, now pending.

FIELD OF THE INVENTION

The present invention relates generally to medical liquid flow in acannula and more particularly to novel structure and methods foroutdwelling selective slit valving of medical liquid flow, includingbi-direction flow, along a cannula, such as a catheter tube or needle,when the distal end thereof is indwelling in a medical patient.

BACKGROUND AND RELATED ART

It has long been recognized to be medically desirable to intravenouslyinfuse liquid into and to sample blood from a patient. Certain problemshave, nevertheless, persisted over the years in the fields ofintravenous (IV) infusion and acquisition of blood specimens.

Typically, during delivery of IV solution to the patient through acannula, such as a catheter tube or IV needle, it is difficult topredict when the supply of IV solution will become exhausted and evenmore difficult to coordinate availability of nursing personnel with theneed to timely disconnect a soon-to-be-dry IV supply from the cathetertube or needle. As a consequence, the distal tip of the cannulasometimes experiences bleedback and clotting. More specifically, in aconventional IV hook-up to a patient, the flow of IV solution occursbecause the force of gravity upon the solution exceeds the bloodpressure in the cardiovascular system of the patient. When the supply ofIV solution is exhausted, the pressure difference changes so that thecardiovascular pressure prevails, causing blood flow into the IVcatheter tube a distance which may vary. Sometimes this blood flowreaches, contaminates and requires replacement of the IV filter. In anyevent, whether the blood reaches the filter or it does not, theaforesaid blood in the catheter will, within a short time, clot. Thisrisks negligent introduction of the clot into the bloodstream andrequires replacement of the IV system, when discovered.

Also, shifting of positions by the patient, as, for example, if thepatient raises the venipuncture site above the IV bottle, sometimescauses refluxing or bleedback of blood into the distal end of thecannula. This reflux may or may not reach the IV filter, but in eitherevent causes IV flow to stop which results in clotting within either thecannula, the filter or both.

When and if discovered, both the clotted IV filter and catheter tube arereplaced with the accompanying patient trauma and expense. It is badpractice and an unacceptable risk to the patient to force a clot fromthe catheter tube into the bloodstream, but, due to negligence, thissometimes happens.

It has been proposed that a one-way outdwelling (outside the patient)standard valve be used to prevent undesired blood flow into the distalend of an indwelling cannula, such as a catheter tube or IV needle.However, this approach does not work in a medically-acceptable fashion.Also, the one-way standard valve will not allow blood sampling when thestandard one way valve is located between the catheter tube and thesampling site.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

In brief summary, the present invention overcomes or substantiallyalleviates the aforesaid problems. The invention comprises noveloutdwelling, normally-closed, pressure-responsive medical slit valveliquid flow controls, and related methods, accommodating flow of liquidincluding, but not limited to, flow of IV solution to the cardiovascularsystem of a medical patient through a cannula, the distal end of whichis indwelling, while preventing bleed-back into and clotting within thecannula and/or IV filter. Thus, cannula and IV filter replacement due tosuch clotting is obviated. The pressure responsive nature of the slitvalve structure prevents the IV system from running dry. Consequently,clots do not form in the cannula and cannot inadvertently be introducedinto the bloodstream.

Stated another way, the present invention provides a pressure-sensitivevalve that opens in response to the high pressure exerted by a full IVsolution bag or bottle but closes as the pressure drops as the bag orbottle empties, which solves or greatly reduces the problem of shuttingoff the IV flow when the bag or bottle runs dry. The valve opens andachieves adequate flow in response to a predetermined pressuredifferential, but closes after the pressure drops to a lowerpredetermined pressure differential.

The present invention accommodates configuration as a two-way valve thatopens in either direction at the same or at different pressuredifferentials, and to allow IV solution in a gravity bag or bottle toflow, shuts off under pressure differential conditions which occur whenthe IV solution bag or bottle runs dry and yet allows intentional bloodsampling across the valve.

Thus, in one presently preferred manifestation of the present invention,the slit valve accommodates bi-directional liquid flow by which bothliquid ingress and blood sampling egress proximal of the slit valve areachieved. It is sometimes desirable for a two-way slit valve flowcontrol embodying the present invention to allow distal flexing to openthe slit for ingress flow at a relatively low pressure differential andproximal flexing to open the slit for egress flow at a relatively highpressure differential.

In a broad sense, the present invention contemplates provision of anoutdwelling, normally closed pressure responsive slit valve by whichliquid is selectively communicated to and from a desired internal bodysite.

Accordingly, it is a primary object of the present invention to overcomeor substantially alleviate some if not all of the above-mentionedmedical liquid flow control problems.

It is a further significant object to provide a novel outdwelling,normally-closed, pressure-responsive slit valve liquid flow control foruse with a medical cannula, and related methods.

Another dominant object is the provision of an outdwelling slit valvestructure, and related methods, accommodating flow of liquid, such as IVsolution, to the cardiovascular system of a medical patient through acannula, such as a peripheral catheter tube, a central venous cathetertube, an arterial catheter tube, or an IV needle, while preventingbleed-back into and clotting within the cannula and obviating anyresulting need for cannula and IV filter replacement.

A further important object is the provision of novel outdwelling,cardiovascular slit valve structure, and related methods, which preventsan associated IV system from running dry.

An additional principal object of the present invention is the provisionof novel outdwelling, two-way slit valve structure, and related methods,for use in achieving selective ingress and egress liquid flow in respectto a desired internal body site of a patient.

A further object of significance is the provision of a novel outdwellingtwo-way normally closed slit valve, and related methods, in which theslit valve is distally flexed, due to a first predetermined pressuredifferential, to accommodate intentional fluid flow to a desiredinternal location in a patient, is closed, due to a second predeterminedpressure differential, and is proximally flexed, due to a third pressuredifferential, to accommodate intentional fluid flow from the internallocation in the patient.

Another valuable object is the provision of a novel outdwelling two-waycardiovascular normally closed slit valve, and related methods, in whichthe slit valve is distally flexed to open a slit for flow to a patientat a relatively low pressure differential across the slit valve and isproximally flexed to open the slit for flow away from the patient at arelatively high pressure differential across the slit valve.

An additional object is the provision of an outdwelling, normally closedslit valve by which liquid is selectively communicated to and from adesired internal body location of a medical patient.

These and other objects and features of the present invention will beapparent from the detailed description taken with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of one presently preferred outdwelling, two way,normally closed, pressure responsive slit valve flow control, embodyingthe principles of the present invention, shown in an installedcondition;

FIG. 2 is an enlarged cross section taken along lines 2--2 of FIG. 1;

FIG. 3 is an enlarged fragmentary cross section of the slit of the flowcontrol of FIG. 1 flexed open in a distal direction due to pressuredifferential P₁ ;

FIG. 4 is similar to FIG. 3 but shows the slit flexed open in a proximaldirection due to pressure differential P₂ ;

FIG. 5 is an enlarged exploded perspective of the slit valve flowcontrol of FIG. 1; and

FIG. 6 is a cross section of a second presently preferred outdwelling,two-way, normally closed, pressure responsive slit valve flow controlfor a peripheral catheter tube, according to the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference is now made to the drawings wherein like numerals are used todesignate like parts throughout. Specifically, FIGS. 1 through 5illustrate one presently preferred two-way, pressure responsive,outdwelling slit valve flow control mechanism or assembly. FIG. 6illustrates a second, presently preferred slit valve flow controlmechanism or assembly. Both of the illustrated embodiments implement theprinciples of the present invention, the slit valve flow controlassembly of FIGS. 1 through 5 being generally designated 10 and the slitvalve flow control mechanism of FIG. 6 being generally designated 12.

Valve assembly 10 is illustrated in FIG. 1 in an "as used" condition,i.e., where the slit valve assembly 10 is interposed between a cannulain the form of a catheter tube, generally designated 14, and anintravenous (IV) tube, generally designated 16. It is to be appreciatedthat the IV use depicted in FIG. 1 is only exemplary and that thepresent invention contemplates outdwelling slit valve control forselective delivery of liquid to and from a desired internal locationwithin a medical patient.

The catheter tube 14, illustrated in FIG. 1, may be of any conventionaltype and is illustrated as having a distal end portion 18 comprising adistal port 20 placed indwelling in the cardiovascular system of amedical patient, namely in the patient's vein 22, as illustrated inFIG. 1. The catheter tube 14 as illustrated in FIGS. 1 and 2 comprises aproximal end portion 24 illustrated, in FIG. 2, as having been force-fitinto suitable liquid communication with the slit valve assembly 10, ashereinafter more fully explained.

Likewise, tube 16 may be of any desired type by which liquid isselectively made available to the slit valve assembly 10. IV tube 16 isillustrated as comprising a distal end portion 26 shown as beingforce-fit into a secured telescopic liquid communicating relationshipwith the slit valve assembly 10, as hereinafter more fully described.Tube 16 is also illustrated in FIG. 1 as comprising a "Y" site 28, wherea hollowed side port 30 emanates. Side port 30 is illustrated as beingclosed at its proximal end by a conventional elastomeric cap 32, whichmay be penetrated by a hypodermic needle, for example, and which willreseal upon removal of the needle. Side port 30 and use of a hypodermicsyringe is one presently preferred way by which a blood specimen may beremoved from or medication introduced into the vein 22 through thecatheter 14 and across the slit valve assembly 10 when predeterminedpressure differential conditions are brought into play.

FIG. 1 further illustrates IV tube 16 as comprising a proximal end 34which is illustrated as being connected via a rigid fitting 35 to an IVbottle 36 shown suspended by a bracket 38 upon a cantilevered arm 40,all of which is conventional. Thus, under predetermined pressuredifferential conditions at slit valve control 10, IV solution in bottle36 is selectively and controllably introduced into the vein 22 fromcatheter tube 14 across slit valve 10, responsive to a predeterminedhydrostatic head.

With reference to FIGS. 2 through 5, slit valve flow control 10 will nowbe described. The slit valve flow control 10 comprises a housing,generally designated 42, illustrated as comprising two parts 44 and 46.Housing parts 44 and 46 are preferably formed of shape-retainingsynthetic resinous material and are constructed so as to be connected,one to the other, as hereinafter more fully explained. Valve housingpart 44 comprises a relatively large annular wall 48, shown as being ofsubstantially uniform thickness and comprising an exposed cylindricalsurface 50 and a concealed inner surface 52. Wall 48 terminates in ablunt, transversely oriented edge 54. Interposed between edge 54 andsurface 52 are internal threads 56, which form an integral part of wall48, as illustrated.

Valve housing part 44 also comprises a transversely oriented, radiallydirected wall 58, which is integral with wall 48 at annular corner 60.Wall 58 is illustrated as having a uniform thickness comprising exposed,external surface 62 and internal surface 64. Wall 48 is interrupted by acentrally disposed aperture 66.

Valve housing part 44 also comprises a distally-extending annular bossin the form of wall 68. Wall 68 is illustrated as having been formed asone piece with, and is, therefore, integral with wall 58 at annularcorner 70. Wall 58 is illustrated as being of uniform thicknessthroughout comprising exterior wall surface 72 and interior wall surface74. Wall 78 terminates in a transversely oriented blunt edge 76. Thediameter of surface 72 is selected, in the illustrated configuration, tobe sufficiently greater than the inside diameter of the proximal end 24of the catheter tube 14 so as to accommodate a satisfactory press-fitrelationship between the two, as illustrated in FIG. 2. For such asatisfactory relationship to exist, sufficient compressive force mustexist between the proximal end 24 of the catheter tube 14 and the wall68 so that inadvertent separation of the two does not occur. Wherepermanent attachment is desired, a suitable bonding agent or adhesivemay be applied between the proximal end 24 of the catheter tube 14 andsurface 72 of wall 68. The diameter of interior surface 74 of wall 68 isselected to accommodate the desired amount of liquid flow therethrough.

Valve housing portion 46 is illustrated as comprising an annular wall80, which comprises a smooth exterior cylindrical surface 82 and asmooth interior surface 84, which is substantially longer in an axialdirection than is surface 82. Surface 82 merges at a 90° angle withradially-directed, exterior surface 86. Wall surface 86 is illustratedas having a radial dimension essentially half that of the radialthickness of wall 80. Wall segment 80 integrally merges with reducedthickness wall segment 88. The interior surface of wall segment 88 isthe previously described surface 84, which merges at a 90° angle withtransversely directed blunt edge 90 of wall segment 88. Wall edgesurface 90 in turn merges substantially at 90° with threaded surface 92of wall segment 88. Threads 92 are sized and arranged so as tothreadedly match previously described threads 56, accommodating threadedjoining of valve housing parts 44 and 46. A suitable adhesive isordinarily placed between threads 56 and 92 to permanently join housingports 44 and 46 after the interior components have been correctly placedtherein.

Wall segment 80 is formed as one piece and, therefore, integrally joinsradially directed wall 94 at annular corner 96. Wall segment 94 isillustrated as being of uniform thickness and as comprising exterior orexposed surface 98 and interior or concealed surface 100.Radially-directed wall 98 is illustrated as being centrally apertured at102.

Valve housing part 46 is further illustrated as comprising aproximally-directed boss in the form of annular wall 104, which isformed as one piece with and is, therefore, integral with radiallydirected wall 94 at corner 106. Wall 104 is illustrated as being ofuniform thickness comprising external cylindrical wall 108 and internalcylindrical wall 110 having a diameter equal to that of aperture 102.Wall segment 104 terminates in transversely directed blunt edge 112 andhas sufficient length and internal diameter to accommodate press-fitacceptance of the rigid male fitting 35 conventionally placed at thedistal end 26 of IV tube 16 so as to preclude inadvertent separation.

Three disc-shaped elements are carried within slit valve flow controlhousing 42 when the two parts 44 and 46 are threadedly secured asillustrated in FIG. 2, namely distal flex control disc 120, proximalflex control disc 122, and central slit diaphragm 124.

Flex control disc 120 is preferably rigid and formed of syntheticresinous materials. Disc 120 is illustrated as comprising a peripheralblunt edge 126 of a disc wall illustrated as being of uniform thicknessthroughout and comprising distal and proximal flat surfaces 128 and 130,respectively. An aperture 132 is centrally disposed through the disc120. The diameter of aperture 132 is selected to allow flexing of thediaphragm 124 in a distal direction, as illustrated in FIG. 3, whensubjected to a positive differential of a predetermined amount (P₁). Theresultant pressure P₁ is ordinarily primarily caused by the hydrostatichead of the IV solution and is set so that the slit closes while adesired amount of IV solution remains in the tube 16 proximal of theslit. While the diameter of the aperture 132 is illustrated in FIG. 2 asbeing substantially the same as the diameter of the bore 74, such doesnot necessarily under all circumstances have to be the case. Also, whilethe surface defining the aperture 132 is illustrated as being axiallydisposed, such surfaces may be diagonally or otherwise disposed so longas diaphragm flexing is accommodated at a desired, relatively lowpressure differential (diagrammatically illustrated as P₁ in FIG. 3). Asillustrated in FIG. 2, in the assembled condition, distal surface 128 ofdisc 120 is contiguous with housing surface 64, while proximal surface130 is contiguous with the distal surface 142 of slit diaphragm 124.

Proximal flex control disc 122 is similar, as illustrated, to disc 120,except the central aperture 132' of disc 122 is of substantially smallerdiameter than the diameter of aperture 132. Since disc 122 is otherwiseillustrated as being the same as disc 120, identical numerals have beenused and no further description is needed. It is to be noted, however,that the diameter of edge 126 of both disc 120 and disc 122 is justslightly less than the diameter of housing surface 52, to accommodateease of assembly.

In the assembled condition, as can be seen clearly from FIGS. 2-4,distal surface 128 of flex control disc 122 is contiguous with theproximal surface 144 of the slit diaphragm 124, while a small area ofthe surface 130 of the flex control disc 122, at the periphery thereof,is contiguous with housing edge 90. It should be readily apparent thatthe discs 120 and 122 compressively support the slit diaphragm 124 inits radial orientation, except to permit the diaphragm 124 to centrallyflex distally and proximally, depending upon pressure differentialconditions. Because the diameter of aperture 132' of disc 122 isillustrated as being materially less than the diameter of aperture 132,central flexing of the diaphragm 124 more readily occurs in a distaldirection than in a proximal direction. Other configurations, however,are within the scope of the present invention.

In the embodiment of FIGS. 1-5, a relatively high pressure differential(diagrammatically illustrated as P₂ in FIG. 4), which flexes thediaphragm 124 proximal into aperture 132' to open slit 146 is requiredto draw blood proximally through the slit 146 of the diaphragm 124,using, for example, a syringe inserted through elastomeric cap 32 atside port 30 of the IV tube 16. In the embodiment of FIG. 4, a lowerpressure differential (diagrammatically illustrated as P₁ in FIG. 3)caused in part by the weight of the IV solution in tube 16, which flexesdiaphragm 124 distally into the larger aperture 132 to open the slit146, is required for IV solution to flow.

Slit diaphragm 124 is disc-shaped and is formed of a suitableelastomeric material, such as silicone rubber. Silicone rubber offersthe advantage of ease in centrally flexing the diaphragm coupled withgood memory characteristics. In an unstressed condition, diaphragm 124is illustrated (in FIG. 2) as being planar and of uniform thickness,comprising edge 140, the unstressed diameter of which is slightly lessthan the diameter of housing wall 52. The diaphragm 124 is illustratedas being of uniform thickness comprising distal, radially-directed flatsurface 142 and proximal, radially-directed flat surface 144.

Diaphragm 124 comprises a centrally-disposed, normally closed,transversely-directed linear slit 146. Slit 146 is illustrated asuniformly extending from surface 142 to surface 144 and is located so asto be directly aligned with previously mentioned apertures 132 and 132',when placed in the assembled position of FIG. 2. The radial length ofslit 146 is selected to accommodate the degree of distal and proximalflexing needed in order to accommodate selective bi-directional liquidflow through the flexed and open slit 146 to introduce, for example, IVsolution into the patient under hydrostatic IV pressure or to removesample blood from the patient under negative pressure or to introducemedication into the bloodstream. In addition to the length of the slit146, the material used to form the diaphragm 124, the thickness of thediaphragm and the size of apertures 132 and 132' individually andcollectively are variables to be set in determining the pressuredifferentials (diagrammatically illustrated in FIGS. 3 and 4 as P₁ andP₂) by which the slit 146 is caused to be opened distally andproximally.

It is also to be appreciated that outdwelling fluid control devicesaccording to the present invention can be free standing, for addition toa cannula, such as a catheter or a needle, at the time of use, or can beconstructed as a component part of an IV cannula system at the time ofmanufacture.

Using the slit valve flow control 10 in conjunction with the rest of thesystem illustrated in FIG. 1, it is to be appreciated that the IV systemnever runs dry because the flexure in a distal direction required atslit 146 (diagrammatically illustrated as P₁ in FIG. 3) ceases to existwhile the IV tube 16 is still partially or entirely filled with IVsolution. Consequently, it is not possible for bleed-back into andclotting within the catheter tube or other IV cannula to occur. Thus,cannula and/or IV filter replacement due to bleed-back contamination isavoided. When blood sampling occurs via side port 30, the presence of IVsolution in the system returns residual blood left in the IV set to thevein 22 immediately following termination of the blood withdrawal cycle.Also, since a blood clot in the cannula, such as catheter tube 14, isnot possible, it is correspondingly impossible for a blood clot to beinadvertently discharged from the catheter tube into the vein.

The same essential result may be accomplished using the slit valve flowcontrol mechanism 12, shown in FIG. 6, in lieu of the slit valve flowcontrol assembly 10 of FIGS. 1 through 5. Slit valve flow controlmechanism 12 comprises a housing 150 comprising two housing parts,generally designated 152 and 154, respectively.

Housing part 152 comprises a wall 156, illustrated as being of uniformthickness. The wall 156 comprises, as illustrated, an upper surface 158,part of which is exposed and part of which is concealed, and a concealedinside surface 168. Wall 156 also comprises an exposed edge surface 160.A male extension 162 projects downwardly from its integral connectionwith wall 156. Extension 162 exteriorly comprises surface 160, a bluntedge 164 and internal surface 166. Thus, wall extension 162 inconjunction with wall 156 forms a recess at internal surface 168. Wall156 and recess at 168 are interrupted by a centrally disposed aperture170, which extends through wall 156. The diameter of aperture 170 isselected so as to accommodate proximal flexing of an associateddiaphragm 220 under a relatively high pressure differential (P₂) forblood sampling, consistent with the preceding description.

Valve part 152 comprises a proximal liquid flow passageway 172.Passageway 172 is defined by a liquid flow port wall, generallydesignated 174. Port wall 174 comprises a lower wall segment 176, shownas having a uniform thickness, which integrally is an extension of wall156 and terminates in a blunt annular edge 178. Proximal port wall 174also comprises a curved wall segment 180, which is also integral in partwith wall 156 and terminates in the previously mentioned blunt edge 178.Directly adjacent blunt edge 178 is a curved segment 181 of the portwall 174, accommodating press-fit internal receipt of rigid fitting 35at the distal end 26 of the IV tube 16, in the manner heretoforementioned. The passageway 172 is sized to accommodate sufficient IV,medication and/or blood sampling flow to accomplish the objectives ofthe invention.

As is the case with housing part 152, housing part 154 is formed as onepiece, preferably of rigid synthetic resinous material. Valve housingpart 154 comprises a wall 190 which comprises an exterior edge 192,which merges at 90° with shoulder 194. Shoulder 194 merges at 90° with areduced diameter surface 196, sized and shaped to press fit against thesurface 166. It is presently preferred that surfaces 166 and 196 bepermanently secured to each other as illustrated using a suitableadhesive. Surface 196 merges through 90° with an abutment surface 198,which has a relatively short transverse distance. Abutment surface 198merges with a downwardly convergent recessed surface 200. Surface 200defines an aperture or orifice 202 at the base thereof which lies in thesame plane as the bottom surface 204 of wall 190.

As can be seen by inspection of FIG. 6, wall surface 204 is partlyexposed and partly concealed. The concealed portion of surface 204 fallswithin a liquid flow passageway 206.

Passageway 206 is defined by liquid port wall structure 208, whichcomprises a thin tube-connecting annular wall extension or lip 210integral with wall 190, and a curved wall 212, which is also integralwith wall 190. Annular wall extension 210 and wall 212 are integral andtogether terminate in blunt edge 214 at the distal end of the passageway206. The exterior surface 216 adjacent edge 214 is of such a diameter toaccommodate external press-fit connection of the proximal end 24 of thecatheter tube 14, in the manner heretofore explained.

From a visual inspection of FIG. 6, it is readily apparent that abutmentsurface 198 is spaced a predetermined distance from surface 168 of wall156 when the housing parts 152 and 154 are fully assembled. The spacebetween surfaces 198 and 168 is preferably slightly less than thethickness of a rectangular diaphragm 220. Rectangular diaphragm 120 isillustrated as being of uniform thickness, preferably slightly more thanthe distance between surfaces 198 and 168 so as to be compression heldbetween surfaces 168 and 198 in the illustrated assembled condition.Diaphragm 220 also comprises a central, normally closed, pressureresponsive linear slit 222 which, under predetermined pressuredifferential conditions selective accommodates bi-directional liquidflow therethrough, flexing in the proximal direction being accommodatedby relatively high proximally directed pressure differential P₂ andflexing to an open position being accommodated in a distal directionunder relatively low distally directed pressure differential P₁, suchdistal flexing being readily accommodated by conical surface 200 ofvalve housing 154.

In terms of use, since the slit valve flow control mechanism 12 isoperatively substantially the same as the already described slit valveflow control mechanism 10, no further operative description is needed.

The invention may be embodied in other specific forms without departmentfrom the spirit or essential characteristics thereof. The presentembodiments, are, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalence of the claims are therefore to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:
 1. Amethod of controlling medical liquid flow in a cannula comprising thesteps of:placing a distal end of the cannula indwelling within aninternal body cavity of a medical patient; connecting a distal end of anoutdwelling slit valve housing directly to a proximal end of the cannulain selective internal medical liquid communication along a predeterminedflow path solely due to pressure differential; causing a substantiallyplanar normally closed slit diaphragm comprising a centrally disposedslit of predetermined length comprising lips normally disposed in tightedge-to-edge relation and otherwise being impervious to be interposedacross the flow path within the housing; connecting a proximal end ofthe outdwelling slit valve housing directly to a distal end of a tubehaving a proximal end connected to an effluent only source of medicalliquid which provides a predetermined distally directed pressure;creating a negative pressure at an outdwelling site proximal of the slitdiaphragm but remote from the source of a magnitude such that thediaphragm is thereby flexed proximally and the lips of the slit areopened proximally to accommodate unidirectional distal-to-proximalmedical liquid flow through the slit from the body cavity of the patientto the remote site.
 2. The method according to claim 1 comprising thefurther step of physically limiting the area of the diaphragm which ispermitted to flex proximally to only a predetermined central portion ofthe total distal area of the diaphragm.
 3. The method according to claim1 comprising the further step of physically altering the pressuredifferential by altering the negative pressure to cause imposition of anopposite predetermined pressure differential across the diaphragmthereby flexing the diaphragm distally, opening the slit therein andcausing proximal-to-distal flow of medical liquid through the slitdirectly from the effluent only source to the patient.
 4. The methodaccording to claim 1 comprising the further step of physically limitingthe area of the diaphragm which is permitted to flex distally to only apredetermined central portion of the distal area of the diaphragm. 5.Two-way valve structure for disposition external of a body of a medicalpatient by which physiological liquid flow to and physiological liquidflow from an internal body cavity site is selectively accomplished, thevalve structure comprising:housing means comprising proximal liquidingress and egress flow port means, distal liquid ingress and egressflow port means and a hollow interior defining a single flow path alongwhich physiological liquid selectively flows; slit valve means sealinglyand transversely disposed within the hollow interior of the housingmeans and comprising substantially planar diaphragm means of generallyuniform thickness in which at least one central normally closed slitcomprising edge-to-edge lips is disposed, the diaphragm means furthercomprising peripheral means imperviously secured to the housing meansand solid means interposed between the peripheral means and the lips,the lips being contiguous in tight edge-to-edge relation when thediaphragm means are unflexed, the diaphragm means being contiguous withfirst and second solid wall means respectively apertured only at acentral location aligned with the slit, the central apertures of thefirst and second solid wall means in combination with said diaphragmmeans accommodating selective flexing of the lips from a tightly closedto an open position in either direction only when either of first andsecond predetermined physiological liquid pressure differentialthresholds is exceeded, the first solid wall means distal of thediaphragm means controlling at least in part the flex and setting onephysiological liquid pressure differential required to open the slit ina distal direction at and solely because of a relatively lowdifferential value and the second solid wall means distal of thediaphragm means controlling at least in part the flex and setting thepressure differential required to open the slit in a proximal directionat and solely because of a relatively high pressure differential value.6. A method of controlling liquid flow to a hollow cannula comprisingthe steps of:causing a normally closed planar slit diaphragm to bedisposed across a flow path in an outdwelling valve structure; placing adistal end of the cannula indwelling within a medical patient;connecting a distal end of the valve structure to the proximal end ofthe cannula, thereby placing the flow path of the valve structure incommunication with the hollow of the cannula; imposing a gravity-causedliquid pressure from a discharge only clean external source of liquiddisposed above the patient for gravity liquid infusion upon a proximalside of the diaphragm; flexing the diaphragm distally only when thecollective liquid pressure upon the diaphragm is distally directed andexceeds a selectively predetermined threshold magnitude; and opening aslit in the diaphragm distally and causing an initial one directionalproximal-to-distal flow of the clean liquid only through the slitdirectly from the discharge only source at least in part under force ofgravity to the cannula and thence to the patient; closing the slit inthe diaphragm to stop liquid infusion before flow reverses when thegravity caused pressure is reduced as liquid from the source is spent.7. A method of controlling uncontaminated medical liquid flow in acannula comprising the steps of:placing a distal end of the cannulaindwelling within a medical patient; connecting a hollow distal end ofan outdwelling slit valve housing to a proximal end of the cannula inselective internal liquid communication along a predetermined liquidflow path; causing a normally closed planar slit diaphragm to besecurely interposed across the flow path within the housing; creating aliquid pressure differential across the diaphragm between a pressureinternal of the patient and a pressure caused at least in part bygravity operating upon a discharge only uncontaminated liquid source;flexing the diaphragm distally when the liquid pressure differential iscontrolled by the pressure of the discharge only source so as to exceeda selectively predetermined threshold pressure without humanintervention; and opening distally the slit in the diaphragm only whilethe flow is proximal-to-distal and causing one way proximal-to-distalflow of uncontaminated liquid through the open slit from the dischargeonly source directly to the patient.
 8. A method of selectivelycontrolling medical liquid flow from a discharge only uncontaminatedmedical liquid source along tubing directly to a patient, comprising thesteps of:placing a distal end of the tubing indwelling within a medicalpatient and connecting the proximal end of the tubing to the source;placing an outdwelling slit valve housing, comprising a planar slitdiaphragm, securely between distal and proximal parts of the tubing tocreate a one-way selectively operable internal liquid communication flowpath directly to the patient; imposing a pressure from within thepatient upon a distal side of the diaphragm; imposing a one-way onlyliquid pressure having at least a gravity component from the dischargeonly source upon a proximal portion of a diaphragm securely disposedwithin the slit valve housing to create a pressure differential which iscontrolled by the pressure of the discharge only source without humanintervention so as to have sufficient selectively predeterminedmagnitude to flex the diaphragm distally to open a slit in the diaphragmand cause proximal-to-distal flow from the discharge only source throughthe slit to the patient along the tubing until the magnitude of thepressure differential falls below the selectively predetermined amount;closing the slit of the diaphragm so as to avoid reflux in response tosaid lowering of the pressure differential below said selectivelypredetermined amount.
 9. A method of selectively controlling medicalliquid flow in tubing comprising the steps of:placing a distal end ofthe tubing indwelling within a medical patient; connecting a distal endof an outdwelling slit valve housing to a proximal end of the tubing inselective internal medical liquid communication along a predeterminedflow path; causing a substantially planar normally closed slit diaphragmcomprising a slit of predetermined length comprising lips normallydisposed in tight edge-to-edge sealed relation and otherwise beingimpervious to be interposed across the flow path within the housing;connecting a one-way source of uncontaminated liquid in one-way flowrelationship only to a proximal end of the housing thereby creating aliquid pressure differential, at least due in part to gravity, of atleast a selectively predetermined magnitude across an area of thediaphragm in which said slit is disposed to only thereby flex thediaphragm distally to unseal and open the lips of the slit and toaccommodate proximal-to-distal uncontaminated medical liquid flow acrossthe open lips of the slit without reflux directly into the tubing andthence directly to the patient, said slit returning to a closed unflexedsealed state when the gravity caused positive liquid pressuredifferential is positive but falls below the selectively predeterminedmagnitude.
 10. A method of selectively controlling medical liquid flowin tubing comprising the steps of:placing a distal end of the tubingindwelling within a medical patient; connecting a distal end of anoutdwelling slit valve housing to a proximal end of the tubing inselective internal medical liquid communication along a predeterminedflow path; causing a substantially planar normally closed slit diaphragmcomprising a slit of predetermined length comprising lips normallydisposed in tight edge-to-edge sealed relation and otherwise beingimpervious to be interposed across the flow path within the housing;connecting a one-way source of uncontaminated liquid in one-way flowrelationship only to a proximal end of the housing thereby creating aliquid pressure differential, at least due in part to gravity, of atleast a selectively predetermined magnitude across an area of thediaphragm in which said slit is disposed to only thereby flex thediaphragm distally and open the lips of the slit and to accommodateproximal-to-distal uncontaminated medical liquid flow across the openlips of the slit directly into the tubing and thence directly to thepatient; altering the liquid pressure differential across the diaphragmcausing the diaphragm to flex proximally, physically limiting the areaof the diaphragm which is permitted to flex proximally to only apredetermined central portion of the proximal area of the diaphragm andcausing distal-to-proximal liquid flow across the diaphragm to a siteother than said one-way source.
 11. Two-way structure for dispositionexternal of a body of a medical patient by which physiological liquidflow to and physiological liquid flow from an internal body site isselectively accomplished, the valve structure comprising:housing meanscomprising proximal liquid ingress and egress flow port means, distalliquid ingress and egress flow port means and a hollow interior defininga single flow path along which physiological liquid flows in a desireddirection; bi-directional displaceable, pressure responsive slit valvemeans sealingly and transversely disposed within the hollow interior ofthe housing means and comprising substantially planar diaphragm means ofgenerally uniform thickness in which at least one central normallyclosed slit comprising edge-to-edge lips is disposed, the diaphragmmeans further comprising peripheral means imperviously secured to thehousing means and solid means interposed between the peripheral meansand the lips, the lips being contiguous in tight edge-to-edge relationwhen the diaphragm means are unflexed, the slit valve means furthercomprising first and second solid wall means respectively apertured onlyat a central location aligned with the slit, the first and second solidwall means being contiguous with the diaphragm means other than at thecentral aperture of each of said first and second solid wall means whenthe diaphragm means are unflexed and which comprise peripheral edgesalso secured to the housing means and control apertures in combinationwith said diaphragm means accommodating selective flexing of the lipsfrom a tightly closed to an open position in either direction only wheneither of first and second predetermined physiological liquid pressuredifferential thresholds is exceeded, the first solid wall means distalof the diaphragm means controlling at least in part the flex and settingone physiological liquid pressure differential required to open the slitin a distal direction at a relatively low differential value and thesecond solid wall means proximal of the diaphragm means controlling atleast in part the flex and setting the pressure differential required toopen the slit in a proximal direction at a relatively high differentialvalue.
 12. Two-way physiological valve structure for dispositionexternal of a body of a medical patient, the valve structurecomprising:housing means comprising proximal physiological liquidingress and egress flow port means, distal physiological liquid ingressand egress flow port means and a hollow interior defining a single flowpath along which physiological liquid entering the port meansselectively flows in a desired direction; bi-directional displaceable,pressure-responsive slit valve means transversely disposed within thehollow interior of the housing means and comprising peripheral meansimperviously secured at the housing means, the slit valve means furthercomprising normally closed slit means with memory comprising opposedlips with contiguous opposed edge held sealingly and alignedly togetherby said memory only when physiological liquid pressure differentialacross the slit valve means is within a predetermined range, the edgesseparating to open the slit valve means only when physiological liquiddifferential pressure is above or below the predetermined range toaccommodate proximal and distal liquid flow respectively along thesingle flow path in a single direction during liquid egress flow and inthe opposite direction during liquid ingress flow; means apertured onlyat the center thereof contiguously associated with slit valve means andalso imperviously secured at the housing means for selectivelydetermining in combination with said slit valve means said predeterminedrange, said range determining means comprising a central aperture andbeing contiguously juxtaposed said slit valve means adjacent to saidcentral aperture.
 13. Valve structure according to claim 12 wherein theslit means comprise an elastomeric diaphragm comprising at least oneslit, the diaphragm being flexed to separate the lip edges only when thephysiological liquid pressure differential is above and below the range.14. Valve structure according to claim 13, wherein the diaphragm is flatand of generally uniform thickness.
 15. Valve structure according toclaim 13 wherein the diaphragm comprises an elastomeric disc.
 16. Valvestructure according to claim 13 wherein the diaphragm is rectangularlyshaped.
 17. Valve structure according to claim 12 wherein the housingmeans comprise at least two parts and releasible fastening means holdingthe two parts together.
 18. Valve structure according to claim 17wherein the two parts are fastened together by threaded connectors. 19.A cardiovascular assembly comprising:first tubing means comprising ahollow interior for placement, at a distal end thereof, in acardiovascular system of a patient; a source of liquid disposed externalof and above the patient by which a first always positive liquidpressure caused at least in part by gravity is created in the assemblyand from which an essentially uncontaminated flow of the liquid isprovided directly to the patient without human manipulation; secondtubing means comprising a hollow interior and distal and proximal endsdisposed external of the patient, the hollow interior of the secondtubing means at the proximal end being in direct communication with thesource liquid at the first liquid pressure; two-way valve structurewithout selectively settable parts contiguously and directly interposedbetween the distal end of the second tubing means and the first tubingmeans at a proximal end thereof external of the patient, a proximal partof the two-way valve structure being in direct communication with theinterior of the second tubing means at the distal end thereof, thesource liquid therein and the first liquid pressure and a distal part ofthe two-way valve structure being only and directly in communicationwith the hollow interior of the first tubing means at a proximal endthereof and a second cardiovascular pressure therein when said firsttubing means are disposed in liquid communication with thecardiovascular system of the patient; the second tubing means furthercomprising means for selectively applying a third pressure across saidtwo-way valve structure; and the two-way valve structure comprisingcentrally interior normally closed bi-directionally pressure-responsiveslit valve means, the slit valve means being imperviously secure at itsperiphery and selectively accommodating only unidirectional flow of apredetermined quantity of liquid across the valve structure directlybetween the first and second tubing means only directly alongselectively openable/closeable centrally disposed flow path means onlyin a proximal to distal direction flow of said predetermined quantity ofliquid to the patient without human manipulation only when the firstpressure exceeds the second by a predetermined magnitude and the thirdpressure is not being imposed, flow in a distal to proximal directionacross the two-way valve structure only when the third pressure controlsand reaches a predetermined amount.
 20. An assembly according to claim19 wherein the slit valve means comprise an elastomeric diaphragm andthe centrally disposed flow path means comprise a central slit havingopposed lips whereby the lips of the slit are flexed open in eitherdirection only when the difference in the first and second pressures isabove a predetermined threshold value.
 21. An assembly according toclaim 20 wherein the diaphragm comprises an elastomeric disc.
 22. Anassembly according to claim 20 wherein the diaphragm is rectangularlyshaped.
 23. An assembly according to claim 19 wherein the two-way valvestructure comprises hollow housing means comprising means whichimperviously secure the slit valve means at the periphery thereof. 24.An assembly according to claim 23 wherein the hollow housing meanscomprise at least two parts fastened together.